Genius

If you are a DirecTV or U-verse subscriber and you link that account up with your wireless account, you will be able to opt for an unlimited data plan—which includes unlimited talk and text—for $100 per month for a single smartphone. Additional smartphones cost $40 each, and the fourth one nets you a credit that makes that line free.

It is not known if this includes tethering.

A paragraph in the article on The Verge states that "'Unlimited' means unfettered access up to 22GB per line," though it is unclear to me if this limitation applies to grandfathered unlimited data plans or to this new unlimited plan as well.

The new AT&T plans will be available starting tomorrow, and I'll either update this post or add a follow-up post as more information becomes available.

Protip: I see no reason why four friends or co-workers (not just four members of the same family) couldn't consolidate their bill to get the cheaper monthly rate.